From 017a3770b3cd663652bc08d0b9abf360c849397c Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Sat, 29 Oct 2022 11:22:01 +0800
Subject: [PATCH] =?UTF-8?q?P4777=20=E3=80=90=E6=A8=A1=E6=9D=BF=E3=80=91?=
 =?UTF-8?q?=E6=89=A9=E5=B1=95=E4=B8=AD=E5=9B=BD=E5=89=A9=E4=BD=99=E5=AE=9A?=
 =?UTF-8?q?=E7=90=86=EF=BC=88EXCRT=EF=BC=89?=
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https://www.luogu.com.cn/record/92007494
---
 Luogu/P4777/P4777.cpp | 37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/Luogu/P4777/P4777.cpp b/Luogu/P4777/P4777.cpp
index 53f3db17..82b80f6e 100644
--- a/Luogu/P4777/P4777.cpp
+++ b/Luogu/P4777/P4777.cpp
@@ -5,25 +5,21 @@ using std::cin;
 using std::cout;
 const char endl = '\n';
 
-const int N = 1e5 + 5;
-
 int n;
 long long a1, b1, a2, b2;
 
-long long exgcd(long long a, long long b, long long& x, long long& y) {
+long long exgcd(long long a, long long b, long long &x, long long &y) {
     if (!b) {
-        x = 1;
-        y = 0;
+        x = 1, y = 0;
+
         return a;
     }
 
     long long g = exgcd(b, a % b, y, x);
-    y -= a / b * x;
-    return g;
-}
 
-long long lcm(long long a, long long b) {
-    return a / std::__gcd(a, b) * b;
+    y -= a / b * x;
+
+    return g;
 }
 
 int main() {
@@ -33,18 +29,17 @@ int main() {
     cin >> n;
 
     for (int i = 1; i <= n; i++) {
-        // $x \equiv a_i (mod b_i)$
-        cin >> a2 >> b2;
+        cin >> b2 >> a2;
 
         if (i == 1) {
-            a1 = a2;
             b1 = b2;
+            a1 = a2;
         } else {
             long long x, y,
-                g = exgcd(a1, a2, x, y),
-                c = b2 - b1,
-                m1 = a2 / g,
-                m2 = lcm(a1, a2);
+                g = exgcd(b1, b2, x, y),
+                c = a2 - a1,
+                m1 = b2 / g,
+                m2 = b1 / g * b2;
 
             if (c % g) {
                 cout << -1 << endl;
@@ -52,13 +47,13 @@ int main() {
                 exit(0);
             }
 
-            x = (static_cast<__int128>(x) * c / g % m1 + m1) % m1;
-            b1 = ((a1 * x + b1) % m2 + m2) % m2;
-            a1 = m2;
+            x = static_cast<__int128>(x) * c / g % m1;
+            a1 = ((a1 + b1 * x) % m2 + m2) % m2;
+            b1 = m2;
         }
     }
 
-    cout << b1 % a1 << endl;
+    cout << a1 % b1 << endl;
 
     return 0;
 }